Did some research and I guess those are big in Michigan, because they grow super fast (7-8' a year) so were thought to be a good plantation pulpwood tree or restoration wildlife habitat tree. But seems most of them die after twenty years or so, being easily susceptible to canker. Best I can tell, hybrid poplar is usually a blend of eastern cottonwood and European black poplar, so in fact not yellow poplar/tulip tree related. Maybe accounts for why it looks a lot less boring than tulip. For all I know, the large cottonwood I milled here might've been a hybrid poplar, which may be a little cooler looking than plain eastern cottonwood.